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Revision 1.155 by root, Sun Jun 14 20:36:59 2009 UTC vs.
Revision 1.278 by root, Sun Oct 1 07:24:34 2017 UTC

1	=head1 NAME	1	=head1 NAME
2		2
3	IO::AIO - Asynchronous Input/Output	3	IO::AIO - Asynchronous/Advanced Input/Output
4		4
5	=head1 SYNOPSIS	5	=head1 SYNOPSIS
6		6
7	use IO::AIO;	7	use IO::AIO;
8		8
9	aio_open "/etc/passwd", O_RDONLY, 0, sub {	9	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
10	my $fh = shift	10	my $fh = shift
11	or die "/etc/passwd: $!";	11	or die "/etc/passwd: $!";
12	...	12	...
13	};	13	};
14		14
…		…
26	$req->cancel; # cancel request if still in queue	26	$req->cancel; # cancel request if still in queue
27		27
28	my $grp = aio_group sub { print "all stats done\n" };	28	my $grp = aio_group sub { print "all stats done\n" };
29	add $grp aio_stat "..." for ...;	29	add $grp aio_stat "..." for ...;
30		30
31	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
32	use AnyEvent::AIO;
33
34	# EV integration
35	my $w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
36
37	# Event integration
38	Event->io (fd => IO::AIO::poll_fileno,
39	poll => 'r',
40	cb => \&IO::AIO::poll_cb);
41
42	# Glib/Gtk2 integration
43	add_watch Glib::IO IO::AIO::poll_fileno,
44	in => sub { IO::AIO::poll_cb; 1 };
45
46	# Tk integration
47	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
48	readable => \&IO::AIO::poll_cb);
49
50	# Danga::Socket integration
51	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
52	\&IO::AIO::poll_cb);
53
54	=head1 DESCRIPTION	31	=head1 DESCRIPTION
55		32
56	This module implements asynchronous I/O using whatever means your	33	This module implements asynchronous I/O using whatever means your
57	operating system supports.	34	operating system supports. It is implemented as an interface to C<libeio>
		35	(L<http://software.schmorp.de/pkg/libeio.html>).
58		36
59	Asynchronous means that operations that can normally block your program	37	Asynchronous means that operations that can normally block your program
60	(e.g. reading from disk) will be done asynchronously: the operation	38	(e.g. reading from disk) will be done asynchronously: the operation
61	will still block, but you can do something else in the meantime. This	39	will still block, but you can do something else in the meantime. This
62	is extremely useful for programs that need to stay interactive even	40	is extremely useful for programs that need to stay interactive even
…		…
66	on a RAID volume or over NFS when you do a number of stat operations	44	on a RAID volume or over NFS when you do a number of stat operations
67	concurrently.	45	concurrently.
68		46
69	While most of this works on all types of file descriptors (for	47	While most of this works on all types of file descriptors (for
70	example sockets), using these functions on file descriptors that	48	example sockets), using these functions on file descriptors that
71	support nonblocking operation (again, sockets, pipes etc.) is very	49	support nonblocking operation (again, sockets, pipes etc.) is
72	inefficient. Use an event loop for that (such as the L<Event|Event>	50	very inefficient. Use an event loop for that (such as the L<EV>
73	module): IO::AIO will naturally fit into such an event loop itself.	51	module): IO::AIO will naturally fit into such an event loop itself.
74		52
75	In this version, a number of threads are started that execute your	53	In this version, a number of threads are started that execute your
76	requests and signal their completion. You don't need thread support	54	requests and signal their completion. You don't need thread support
77	in perl, and the threads created by this module will not be visible	55	in perl, and the threads created by this module will not be visible
…		…
80	not well-supported or restricted (GNU/Linux doesn't allow them on normal	58	not well-supported or restricted (GNU/Linux doesn't allow them on normal
81	files currently, for example), and they would only support aio_read and	59	files currently, for example), and they would only support aio_read and
82	aio_write, so the remaining functionality would have to be implemented	60	aio_write, so the remaining functionality would have to be implemented
83	using threads anyway.	61	using threads anyway.
84		62
		63	In addition to asynchronous I/O, this module also exports some rather
		64	arcane interfaces, such as C<madvise> or linux's C<splice> system call,
		65	which is why the C<A> in C<AIO> can also mean I<advanced>.
		66
85	Although the module will work in the presence of other (Perl-) threads,	67	Although the module will work in the presence of other (Perl-) threads,
86	it is currently not reentrant in any way, so use appropriate locking	68	it is currently not reentrant in any way, so use appropriate locking
87	yourself, always call C<poll_cb> from within the same thread, or never	69	yourself, always call C<poll_cb> from within the same thread, or never
88	call C<poll_cb> (or other C<aio_> functions) recursively.	70	call C<poll_cb> (or other C<aio_> functions) recursively.
89		71
90	=head2 EXAMPLE	72	=head2 EXAMPLE
91		73
92	This is a simple example that uses the Event module and loads	74	This is a simple example that uses the EV module and loads
93	F</etc/passwd> asynchronously:	75	F</etc/passwd> asynchronously:
94		76
95	use Fcntl;
96	use Event;	77	use EV;
97	use IO::AIO;	78	use IO::AIO;
98		79
99	# register the IO::AIO callback with Event	80	# register the IO::AIO callback with EV
100	Event->io (fd => IO::AIO::poll_fileno,	81	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
101	poll => 'r',
102	cb => \&IO::AIO::poll_cb);
103		82
104	# queue the request to open /etc/passwd	83	# queue the request to open /etc/passwd
105	aio_open "/etc/passwd", O_RDONLY, 0, sub {	84	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
106	my $fh = shift	85	my $fh = shift
107	or die "error while opening: $!";	86	or die "error while opening: $!";
108		87
109	# stat'ing filehandles is generally non-blocking	88	# stat'ing filehandles is generally non-blocking
110	my $size = -s $fh;	89	my $size = -s $fh;
…		…
119		98
120	# file contents now in $contents	99	# file contents now in $contents
121	print $contents;	100	print $contents;
122		101
123	# exit event loop and program	102	# exit event loop and program
124	Event::unloop;	103	EV::break;
125	};	104	};
126	};	105	};
127		106
128	# possibly queue up other requests, or open GUI windows,	107	# possibly queue up other requests, or open GUI windows,
129	# check for sockets etc. etc.	108	# check for sockets etc. etc.
130		109
131	# process events as long as there are some:	110	# process events as long as there are some:
132	Event::loop;	111	EV::run;
133		112
134	=head1 REQUEST ANATOMY AND LIFETIME	113	=head1 REQUEST ANATOMY AND LIFETIME
135		114
136	Every C<aio_*> function creates a request. which is a C data structure not	115	Every C<aio_*> function creates a request. which is a C data structure not
137	directly visible to Perl.	116	directly visible to Perl.
…		…
187		166
188	package IO::AIO;	167	package IO::AIO;
189		168
190	use Carp ();	169	use Carp ();
191		170
192	no warnings;	171	use common::sense;
193	use strict 'vars';
194		172
195	use base 'Exporter';	173	use base 'Exporter';
196		174
197	BEGIN {	175	BEGIN {
198	our $VERSION = '3.23';	176	our $VERSION = 4.35;
199		177
200	our @AIO_REQ = qw(aio_sendfile aio_read aio_write aio_open aio_close	178	our @AIO_REQ = qw(aio_sendfile aio_seek aio_read aio_write aio_open aio_close
201	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx	179	aio_stat aio_lstat aio_unlink aio_rmdir aio_readdir aio_readdirx
202	aio_scandir aio_symlink aio_readlink aio_sync aio_fsync	180	aio_scandir aio_symlink aio_readlink aio_realpath aio_fcntl aio_ioctl
203	aio_fdatasync aio_sync_file_range aio_pathsync aio_readahead	181	aio_sync aio_fsync aio_syncfs aio_fdatasync aio_sync_file_range
		182	aio_pathsync aio_readahead aio_fiemap aio_allocate
204	aio_rename aio_link aio_move aio_copy aio_group	183	aio_rename aio_rename2 aio_link aio_move aio_copy aio_group
205	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown	184	aio_nop aio_mknod aio_load aio_rmtree aio_mkdir aio_chown
206	aio_chmod aio_utime aio_truncate);	185	aio_chmod aio_utime aio_truncate
		186	aio_msync aio_mtouch aio_mlock aio_mlockall
		187	aio_statvfs
		188	aio_wd);
207		189
208	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));	190	our @EXPORT = (@AIO_REQ, qw(aioreq_pri aioreq_nice));
209	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush	191	our @EXPORT_OK = qw(poll_fileno poll_cb poll_wait flush
210	min_parallel max_parallel max_idle	192	min_parallel max_parallel max_idle idle_timeout
211	nreqs nready npending nthreads	193	nreqs nready npending nthreads
212	max_poll_time max_poll_reqs);	194	max_poll_time max_poll_reqs
		195	sendfile fadvise madvise
		196	mmap munmap munlock munlockall);
213		197
214	push @AIO_REQ, qw(aio_busy); # not exported	198	push @AIO_REQ, qw(aio_busy); # not exported
215		199
216	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';	200	@IO::AIO::GRP::ISA = 'IO::AIO::REQ';
217		201
…		…
219	XSLoader::load ("IO::AIO", $VERSION);	203	XSLoader::load ("IO::AIO", $VERSION);
220	}	204	}
221		205
222	=head1 FUNCTIONS	206	=head1 FUNCTIONS
223		207
224	=head2 AIO REQUEST FUNCTIONS	208	=head2 QUICK OVERVIEW
		209
		210	This section simply lists the prototypes most of the functions for
		211	quick reference. See the following sections for function-by-function
		212	documentation.
		213
		214	aio_wd $pathname, $callback->($wd)
		215	aio_open $pathname, $flags, $mode, $callback->($fh)
		216	aio_close $fh, $callback->($status)
		217	aio_seek $fh,$offset,$whence, $callback->($offs)
		218	aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		219	aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
		220	aio_sendfile $out_fh, $in_fh, $in_offset, $length, $callback->($retval)
		221	aio_readahead $fh,$offset,$length, $callback->($retval)
		222	aio_stat $fh_or_path, $callback->($status)
		223	aio_lstat $fh, $callback->($status)
		224	aio_statvfs $fh_or_path, $callback->($statvfs)
		225	aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
		226	aio_chown $fh_or_path, $uid, $gid, $callback->($status)
		227	aio_chmod $fh_or_path, $mode, $callback->($status)
		228	aio_truncate $fh_or_path, $offset, $callback->($status)
		229	aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		230	aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		231	aio_unlink $pathname, $callback->($status)
		232	aio_mknod $pathname, $mode, $dev, $callback->($status)
		233	aio_link $srcpath, $dstpath, $callback->($status)
		234	aio_symlink $srcpath, $dstpath, $callback->($status)
		235	aio_readlink $pathname, $callback->($link)
		236	aio_realpath $pathname, $callback->($path)
		237	aio_rename $srcpath, $dstpath, $callback->($status)
		238	aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		239	aio_mkdir $pathname, $mode, $callback->($status)
		240	aio_rmdir $pathname, $callback->($status)
		241	aio_readdir $pathname, $callback->($entries)
		242	aio_readdirx $pathname, $flags, $callback->($entries, $flags)
		243	IO::AIO::READDIR_DENTS IO::AIO::READDIR_DIRS_FIRST
		244	IO::AIO::READDIR_STAT_ORDER IO::AIO::READDIR_FOUND_UNKNOWN
		245	aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
		246	aio_load $pathname, $data, $callback->($status)
		247	aio_copy $srcpath, $dstpath, $callback->($status)
		248	aio_move $srcpath, $dstpath, $callback->($status)
		249	aio_rmtree $pathname, $callback->($status)
		250	aio_fcntl $fh, $cmd, $arg, $callback->($status)
		251	aio_ioctl $fh, $request, $buf, $callback->($status)
		252	aio_sync $callback->($status)
		253	aio_syncfs $fh, $callback->($status)
		254	aio_fsync $fh, $callback->($status)
		255	aio_fdatasync $fh, $callback->($status)
		256	aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
		257	aio_pathsync $pathname, $callback->($status)
		258	aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		259	aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		260	aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		261	aio_mlockall $flags, $callback->($status)
		262	aio_group $callback->(...)
		263	aio_nop $callback->()
		264
		265	$prev_pri = aioreq_pri [$pri]
		266	aioreq_nice $pri_adjust
		267
		268	IO::AIO::poll_wait
		269	IO::AIO::poll_cb
		270	IO::AIO::poll
		271	IO::AIO::flush
		272	IO::AIO::max_poll_reqs $nreqs
		273	IO::AIO::max_poll_time $seconds
		274	IO::AIO::min_parallel $nthreads
		275	IO::AIO::max_parallel $nthreads
		276	IO::AIO::max_idle $nthreads
		277	IO::AIO::idle_timeout $seconds
		278	IO::AIO::max_outstanding $maxreqs
		279	IO::AIO::nreqs
		280	IO::AIO::nready
		281	IO::AIO::npending
		282	$nfd = IO::AIO::get_fdlimit [EXPERIMENTAL]
		283	IO::AIO::min_fdlimit $nfd [EXPERIMENTAL]
		284
		285	IO::AIO::sendfile $ofh, $ifh, $offset, $count
		286	IO::AIO::fadvise $fh, $offset, $len, $advice
		287	IO::AIO::mmap $scalar, $length, $prot, $flags[, $fh[, $offset]]
		288	IO::AIO::munmap $scalar
		289	IO::AIO::madvise $scalar, $offset, $length, $advice
		290	IO::AIO::mprotect $scalar, $offset, $length, $protect
		291	IO::AIO::munlock $scalar, $offset = 0, $length = undef
		292	IO::AIO::munlockall
		293
		294	=head2 API NOTES
225		295
226	All the C<aio_*> calls are more or less thin wrappers around the syscall	296	All the C<aio_*> calls are more or less thin wrappers around the syscall
227	with the same name (sans C<aio_>). The arguments are similar or identical,	297	with the same name (sans C<aio_>). The arguments are similar or identical,
228	and they all accept an additional (and optional) C<$callback> argument	298	and they all accept an additional (and optional) C<$callback> argument
229	which must be a code reference. This code reference will get called with	299	which must be a code reference. This code reference will be called after
230	the syscall return code (e.g. most syscalls return C<-1> on error, unlike	300	the syscall has been executed in an asynchronous fashion. The results
231	perl, which usually delivers "false") as its sole argument after the given	301	of the request will be passed as arguments to the callback (and, if an
232	syscall has been executed asynchronously.	302	error occured, in C<$!>) - for most requests the syscall return code (e.g.
		303	most syscalls return C<-1> on error, unlike perl, which usually delivers
		304	"false").
		305
		306	Some requests (such as C<aio_readdir>) pass the actual results and
		307	communicate failures by passing C<undef>.
233		308
234	All functions expecting a filehandle keep a copy of the filehandle	309	All functions expecting a filehandle keep a copy of the filehandle
235	internally until the request has finished.	310	internally until the request has finished.
236		311
237	All functions return request objects of type L<IO::AIO::REQ> that allow	312	All functions return request objects of type L<IO::AIO::REQ> that allow
238	further manipulation of those requests while they are in-flight.	313	further manipulation of those requests while they are in-flight.
239		314
240	The pathnames you pass to these routines I<must> be absolute and	315	The pathnames you pass to these routines I<should> be absolute. The
241	encoded as octets. The reason for the former is that at the time the	316	reason for this is that at the time the request is being executed, the
242	request is being executed, the current working directory could have	317	current working directory could have changed. Alternatively, you can
243	changed. Alternatively, you can make sure that you never change the	318	make sure that you never change the current working directory anywhere
244	current working directory anywhere in the program and then use relative	319	in the program and then use relative paths. You can also take advantage
245	paths.	320	of IO::AIOs working directory abstraction, that lets you specify paths
		321	relative to some previously-opened "working directory object" - see the
		322	description of the C<IO::AIO::WD> class later in this document.
246		323
247	To encode pathnames as octets, either make sure you either: a) always pass	324	To encode pathnames as octets, either make sure you either: a) always pass
248	in filenames you got from outside (command line, readdir etc.) without	325	in filenames you got from outside (command line, readdir etc.) without
249	tinkering, b) are ASCII or ISO 8859-1, c) use the Encode module and encode	326	tinkering, b) are in your native filesystem encoding, c) use the Encode
250	your pathnames to the locale (or other) encoding in effect in the user	327	module and encode your pathnames to the locale (or other) encoding in
251	environment, d) use Glib::filename_from_unicode on unicode filenames or e)	328	effect in the user environment, d) use Glib::filename_from_unicode on
252	use something else to ensure your scalar has the correct contents.	329	unicode filenames or e) use something else to ensure your scalar has the
		330	correct contents.
253		331
254	This works, btw. independent of the internal UTF-8 bit, which IO::AIO	332	This works, btw. independent of the internal UTF-8 bit, which IO::AIO
255	handles correctly whether it is set or not.	333	handles correctly whether it is set or not.
		334
		335	=head2 AIO REQUEST FUNCTIONS
256		336
257	=over 4	337	=over 4
258		338
259	=item $prev_pri = aioreq_pri [$pri]	339	=item $prev_pri = aioreq_pri [$pri]
260		340
…		…
290		370
291		371
292	=item aio_open $pathname, $flags, $mode, $callback->($fh)	372	=item aio_open $pathname, $flags, $mode, $callback->($fh)
293		373
294	Asynchronously open or create a file and call the callback with a newly	374	Asynchronously open or create a file and call the callback with a newly
295	created filehandle for the file.	375	created filehandle for the file (or C<undef> in case of an error).
296		376
297	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,	377	The pathname passed to C<aio_open> must be absolute. See API NOTES, above,
298	for an explanation.	378	for an explanation.
299		379
300	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a	380	The C<$flags> argument is a bitmask. See the C<Fcntl> module for a
…		…
307	by the umask in effect then the request is being executed, so better never	387	by the umask in effect then the request is being executed, so better never
308	change the umask.	388	change the umask.
309		389
310	Example:	390	Example:
311		391
312	aio_open "/etc/passwd", O_RDONLY, 0, sub {	392	aio_open "/etc/passwd", IO::AIO::O_RDONLY, 0, sub {
313	if ($_[0]) {	393	if ($_[0]) {
314	print "open successful, fh is $_[0]\n";	394	print "open successful, fh is $_[0]\n";
315	...	395	...
316	} else {	396	} else {
317	die "open failed: $!\n";	397	die "open failed: $!\n";
318	}	398	}
319	};	399	};
320		400
		401	In addition to all the common open modes/flags (C<O_RDONLY>, C<O_WRONLY>,
		402	C<O_RDWR>, C<O_CREAT>, C<O_TRUNC>, C<O_EXCL> and C<O_APPEND>), the
		403	following POSIX and non-POSIX constants are available (missing ones on
		404	your system are, as usual, C<0>):
		405
		406	C<O_ASYNC>, C<O_DIRECT>, C<O_NOATIME>, C<O_CLOEXEC>, C<O_NOCTTY>, C<O_NOFOLLOW>,
		407	C<O_NONBLOCK>, C<O_EXEC>, C<O_SEARCH>, C<O_DIRECTORY>, C<O_DSYNC>,
		408	C<O_RSYNC>, C<O_SYNC>, C<O_PATH>, C<O_TMPFILE>, and C<O_TTY_INIT>.
		409
321		410
322	=item aio_close $fh, $callback->($status)	411	=item aio_close $fh, $callback->($status)
323		412
324	Asynchronously close a file and call the callback with the result	413	Asynchronously close a file and call the callback with the result
325	code.	414	code.
…		…
334	Or in other words: the file descriptor will be closed, but it will not be	423	Or in other words: the file descriptor will be closed, but it will not be
335	free for reuse until the perl filehandle is closed.	424	free for reuse until the perl filehandle is closed.
336		425
337	=cut	426	=cut
338		427
		428	=item aio_seek $fh, $offset, $whence, $callback->($offs)
		429
		430	Seeks the filehandle to the new C<$offset>, similarly to perl's
		431	C<sysseek>. The C<$whence> can use the traditional values (C<0> for
		432	C<IO::AIO::SEEK_SET>, C<1> for C<IO::AIO::SEEK_CUR> or C<2> for
		433	C<IO::AIO::SEEK_END>).
		434
		435	The resulting absolute offset will be passed to the callback, or C<-1> in
		436	case of an error.
		437
		438	In theory, the C<$whence> constants could be different than the
		439	corresponding values from L<Fcntl>, but perl guarantees they are the same,
		440	so don't panic.
		441
		442	As a GNU/Linux (and maybe Solaris) extension, also the constants
		443	C<IO::AIO::SEEK_DATA> and C<IO::AIO::SEEK_HOLE> are available, if they
		444	could be found. No guarantees about suitability for use in C<aio_seek> or
		445	Perl's C<sysseek> can be made though, although I would naively assume they
		446	"just work".
		447
339	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	448	=item aio_read $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
340		449
341	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)	450	=item aio_write $fh,$offset,$length, $data,$dataoffset, $callback->($retval)
342		451
343	Reads or writes C<$length> bytes from or to the specified C<$fh> and	452	Reads or writes C<$length> bytes from or to the specified C<$fh> and
344	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset>	453	C<$offset> into the scalar given by C<$data> and offset C<$dataoffset> and
345	and calls the callback without the actual number of bytes read (or -1 on	454	calls the callback with the actual number of bytes transferred (or -1 on
346	error, just like the syscall).	455	error, just like the syscall).
347		456
348	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to	457	C<aio_read> will, like C<sysread>, shrink or grow the C<$data> scalar to
349	offset plus the actual number of bytes read.	458	offset plus the actual number of bytes read.
350		459
…		…
375		484
376	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts	485	Tries to copy C<$length> bytes from C<$in_fh> to C<$out_fh>. It starts
377	reading at byte offset C<$in_offset>, and starts writing at the current	486	reading at byte offset C<$in_offset>, and starts writing at the current
378	file offset of C<$out_fh>. Because of that, it is not safe to issue more	487	file offset of C<$out_fh>. Because of that, it is not safe to issue more
379	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each	488	than one C<aio_sendfile> per C<$out_fh>, as they will interfere with each
380	other.	489	other. The same C<$in_fh> works fine though, as this function does not
		490	move or use the file offset of C<$in_fh>.
381		491
		492	Please note that C<aio_sendfile> can read more bytes from C<$in_fh> than
		493	are written, and there is no way to find out how many more bytes have been
		494	read from C<aio_sendfile> alone, as C<aio_sendfile> only provides the
		495	number of bytes written to C<$out_fh>. Only if the result value equals
		496	C<$length> one can assume that C<$length> bytes have been read.
		497
		498	Unlike with other C<aio_> functions, it makes a lot of sense to use
		499	C<aio_sendfile> on non-blocking sockets, as long as one end (typically
		500	the C<$in_fh>) is a file - the file I/O will then be asynchronous, while
		501	the socket I/O will be non-blocking. Note, however, that you can run
		502	into a trap where C<aio_sendfile> reads some data with readahead, then
		503	fails to write all data, and when the socket is ready the next time, the
		504	data in the cache is already lost, forcing C<aio_sendfile> to again hit
		505	the disk. Explicit C<aio_read> + C<aio_write> let's you better control
		506	resource usage.
		507
382	This call tries to make use of a native C<sendfile> syscall to provide	508	This call tries to make use of a native C<sendfile>-like syscall to
383	zero-copy operation. For this to work, C<$out_fh> should refer to a	509	provide zero-copy operation. For this to work, C<$out_fh> should refer to
384	socket, and C<$in_fh> should refer to mmap'able file.	510	a socket, and C<$in_fh> should refer to an mmap'able file.
385		511
386	If the native sendfile call fails or is not implemented, it will be	512	If a native sendfile cannot be found or it fails with C<ENOSYS>,
387	emulated, so you can call C<aio_sendfile> on any type of filehandle	513	C<EINVAL>, C<ENOTSUP>, C<EOPNOTSUPP>, C<EAFNOSUPPORT>, C<EPROTOTYPE> or
		514	C<ENOTSOCK>, it will be emulated, so you can call C<aio_sendfile> on any
388	regardless of the limitations of the operating system.	515	type of filehandle regardless of the limitations of the operating system.
389		516
390	Please note, however, that C<aio_sendfile> can read more bytes from	517	As native sendfile syscalls (as practically any non-POSIX interface hacked
391	C<$in_fh> than are written, and there is no way to find out how many	518	together in a hurry to improve benchmark numbers) tend to be rather buggy
392	bytes have been read from C<aio_sendfile> alone, as C<aio_sendfile> only	519	on many systems, this implementation tries to work around some known bugs
393	provides the number of bytes written to C<$out_fh>. Only if the result	520	in Linux and FreeBSD kernels (probably others, too), but that might fail,
394	value equals C<$length> one can assume that C<$length> bytes have been	521	so you really really should check the return value of C<aio_sendfile> -
395	read.	522	fewer bytes than expected might have been transferred.
396		523
397		524
398	=item aio_readahead $fh,$offset,$length, $callback->($retval)	525	=item aio_readahead $fh,$offset,$length, $callback->($retval)
399		526
400	C<aio_readahead> populates the page cache with data from a file so that	527	C<aio_readahead> populates the page cache with data from a file so that
…		…
404	whole pages, so that offset is effectively rounded down to a page boundary	531	whole pages, so that offset is effectively rounded down to a page boundary
405	and bytes are read up to the next page boundary greater than or equal to	532	and bytes are read up to the next page boundary greater than or equal to
406	(off-set+length). C<aio_readahead> does not read beyond the end of the	533	(off-set+length). C<aio_readahead> does not read beyond the end of the
407	file. The current file offset of the file is left unchanged.	534	file. The current file offset of the file is left unchanged.
408		535
409	If that syscall doesn't exist (likely if your OS isn't Linux) it will be	536	If that syscall doesn't exist (likely if your kernel isn't Linux) it will
410	emulated by simply reading the data, which would have a similar effect.	537	be emulated by simply reading the data, which would have a similar effect.
411		538
412		539
413	=item aio_stat $fh_or_path, $callback->($status)	540	=item aio_stat $fh_or_path, $callback->($status)
414		541
415	=item aio_lstat $fh, $callback->($status)	542	=item aio_lstat $fh, $callback->($status)
…		…
422	for an explanation.	549	for an explanation.
423		550
424	Currently, the stats are always 64-bit-stats, i.e. instead of returning an	551	Currently, the stats are always 64-bit-stats, i.e. instead of returning an
425	error when stat'ing a large file, the results will be silently truncated	552	error when stat'ing a large file, the results will be silently truncated
426	unless perl itself is compiled with large file support.	553	unless perl itself is compiled with large file support.
		554
		555	To help interpret the mode and dev/rdev stat values, IO::AIO offers the
		556	following constants and functions (if not implemented, the constants will
		557	be C<0> and the functions will either C<croak> or fall back on traditional
		558	behaviour).
		559
		560	C<S_IFMT>, C<S_IFIFO>, C<S_IFCHR>, C<S_IFBLK>, C<S_IFLNK>, C<S_IFREG>,
		561	C<S_IFDIR>, C<S_IFWHT>, C<S_IFSOCK>, C<IO::AIO::major $dev_t>,
		562	C<IO::AIO::minor $dev_t>, C<IO::AIO::makedev $major, $minor>.
427		563
428	Example: Print the length of F</etc/passwd>:	564	Example: Print the length of F</etc/passwd>:
429		565
430	aio_stat "/etc/passwd", sub {	566	aio_stat "/etc/passwd", sub {
431	$_[0] and die "stat failed: $!";	567	$_[0] and die "stat failed: $!";
432	print "size is ", -s _, "\n";	568	print "size is ", -s _, "\n";
433	};	569	};
434		570
435		571
		572	=item aio_statvfs $fh_or_path, $callback->($statvfs)
		573
		574	Works like the POSIX C<statvfs> or C<fstatvfs> syscalls, depending on
		575	whether a file handle or path was passed.
		576
		577	On success, the callback is passed a hash reference with the following
		578	members: C<bsize>, C<frsize>, C<blocks>, C<bfree>, C<bavail>, C<files>,
		579	C<ffree>, C<favail>, C<fsid>, C<flag> and C<namemax>. On failure, C<undef>
		580	is passed.
		581
		582	The following POSIX IO::AIO::ST_* constants are defined: C<ST_RDONLY> and
		583	C<ST_NOSUID>.
		584
		585	The following non-POSIX IO::AIO::ST_* flag masks are defined to
		586	their correct value when available, or to C<0> on systems that do
		587	not support them: C<ST_NODEV>, C<ST_NOEXEC>, C<ST_SYNCHRONOUS>,
		588	C<ST_MANDLOCK>, C<ST_WRITE>, C<ST_APPEND>, C<ST_IMMUTABLE>, C<ST_NOATIME>,
		589	C<ST_NODIRATIME> and C<ST_RELATIME>.
		590
		591	Example: stat C</wd> and dump out the data if successful.
		592
		593	aio_statvfs "/wd", sub {
		594	my $f = $_[0]
		595	or die "statvfs: $!";
		596
		597	use Data::Dumper;
		598	say Dumper $f;
		599	};
		600
		601	# result:
		602	{
		603	bsize => 1024,
		604	bfree => 4333064312,
		605	blocks => 10253828096,
		606	files => 2050765568,
		607	flag => 4096,
		608	favail => 2042092649,
		609	bavail => 4333064312,
		610	ffree => 2042092649,
		611	namemax => 255,
		612	frsize => 1024,
		613	fsid => 1810
		614	}
		615
		616	Here is a (likely partial - send me updates!) list of fsid values used by
		617	Linux - it is safe to hardcode these when C<$^O> is C<linux>:
		618
		619	0x0000adf5 adfs
		620	0x0000adff affs
		621	0x5346414f afs
		622	0x09041934 anon-inode filesystem
		623	0x00000187 autofs
		624	0x42465331 befs
		625	0x1badface bfs
		626	0x42494e4d binfmt_misc
		627	0x9123683e btrfs
		628	0x0027e0eb cgroupfs
		629	0xff534d42 cifs
		630	0x73757245 coda
		631	0x012ff7b7 coh
		632	0x28cd3d45 cramfs
		633	0x453dcd28 cramfs-wend (wrong endianness)
		634	0x64626720 debugfs
		635	0x00001373 devfs
		636	0x00001cd1 devpts
		637	0x0000f15f ecryptfs
		638	0x00414a53 efs
		639	0x0000137d ext
		640	0x0000ef53 ext2/ext3/ext4
		641	0x0000ef51 ext2
		642	0xf2f52010 f2fs
		643	0x00004006 fat
		644	0x65735546 fuseblk
		645	0x65735543 fusectl
		646	0x0bad1dea futexfs
		647	0x01161970 gfs2
		648	0x47504653 gpfs
		649	0x00004244 hfs
		650	0xf995e849 hpfs
		651	0x00c0ffee hostfs
		652	0x958458f6 hugetlbfs
		653	0x2bad1dea inotifyfs
		654	0x00009660 isofs
		655	0x000072b6 jffs2
		656	0x3153464a jfs
		657	0x6b414653 k-afs
		658	0x0bd00bd0 lustre
		659	0x0000137f minix
		660	0x0000138f minix 30 char names
		661	0x00002468 minix v2
		662	0x00002478 minix v2 30 char names
		663	0x00004d5a minix v3
		664	0x19800202 mqueue
		665	0x00004d44 msdos
		666	0x0000564c novell
		667	0x00006969 nfs
		668	0x6e667364 nfsd
		669	0x00003434 nilfs
		670	0x5346544e ntfs
		671	0x00009fa1 openprom
		672	0x7461636F ocfs2
		673	0x00009fa0 proc
		674	0x6165676c pstorefs
		675	0x0000002f qnx4
		676	0x68191122 qnx6
		677	0x858458f6 ramfs
		678	0x52654973 reiserfs
		679	0x00007275 romfs
		680	0x67596969 rpc_pipefs
		681	0x73636673 securityfs
		682	0xf97cff8c selinux
		683	0x0000517b smb
		684	0x534f434b sockfs
		685	0x73717368 squashfs
		686	0x62656572 sysfs
		687	0x012ff7b6 sysv2
		688	0x012ff7b5 sysv4
		689	0x01021994 tmpfs
		690	0x15013346 udf
		691	0x00011954 ufs
		692	0x54190100 ufs byteswapped
		693	0x00009fa2 usbdevfs
		694	0x01021997 v9fs
		695	0xa501fcf5 vxfs
		696	0xabba1974 xenfs
		697	0x012ff7b4 xenix
		698	0x58465342 xfs
		699	0x012fd16d xia
		700
436	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)	701	=item aio_utime $fh_or_path, $atime, $mtime, $callback->($status)
437		702
438	Works like perl's C<utime> function (including the special case of $atime	703	Works like perl's C<utime> function (including the special case of $atime
439	and $mtime being undef). Fractional times are supported if the underlying	704	and $mtime being undef). Fractional times are supported if the underlying
440	syscalls support them.	705	syscalls support them.
…		…
467	=item aio_truncate $fh_or_path, $offset, $callback->($status)	732	=item aio_truncate $fh_or_path, $offset, $callback->($status)
468		733
469	Works like truncate(2) or ftruncate(2).	734	Works like truncate(2) or ftruncate(2).
470		735
471		736
		737	=item aio_allocate $fh, $mode, $offset, $len, $callback->($status)
		738
		739	Allocates or frees disk space according to the C<$mode> argument. See the
		740	linux C<fallocate> documentation for details.
		741
		742	C<$mode> is usually C<0> or C<IO::AIO::FALLOC_FL_KEEP_SIZE> to allocate
		743	space, or C<IO::AIO::FALLOC_FL_PUNCH_HOLE | IO::AIO::FALLOC_FL_KEEP_SIZE>,
		744	to deallocate a file range.
		745
		746	IO::AIO also supports C<FALLOC_FL_COLLAPSE_RANGE>, to remove a range
		747	(without leaving a hole), C<FALLOC_FL_ZERO_RANGE>, to zero a range,
		748	C<FALLOC_FL_INSERT_RANGE> to insert a range and C<FALLOC_FL_UNSHARE_RANGE>
		749	to unshare shared blocks (see your L<fallocate(2)> manpage).
		750
		751	The file system block size used by C<fallocate> is presumably the
		752	C<f_bsize> returned by C<statvfs>, but different filesystems and filetypes
		753	can dictate other limitations.
		754
		755	If C<fallocate> isn't available or cannot be emulated (currently no
		756	emulation will be attempted), passes C<-1> and sets C<$!> to C<ENOSYS>.
		757
		758
472	=item aio_chmod $fh_or_path, $mode, $callback->($status)	759	=item aio_chmod $fh_or_path, $mode, $callback->($status)
473		760
474	Works like perl's C<chmod> function.	761	Works like perl's C<chmod> function.
475		762
476		763
…		…
478		765
479	Asynchronously unlink (delete) a file and call the callback with the	766	Asynchronously unlink (delete) a file and call the callback with the
480	result code.	767	result code.
481		768
482		769
483	=item aio_mknod $path, $mode, $dev, $callback->($status)	770	=item aio_mknod $pathname, $mode, $dev, $callback->($status)
484		771
485	[EXPERIMENTAL]	772	[EXPERIMENTAL]
486		773
487	Asynchronously create a device node (or fifo). See mknod(2).	774	Asynchronously create a device node (or fifo). See mknod(2).
488		775
489	The only (POSIX-) portable way of calling this function is:	776	The only (POSIX-) portable way of calling this function is:
490		777
491	aio_mknod $path, IO::AIO::S_IFIFO | $mode, 0, sub { ...	778	aio_mknod $pathname, IO::AIO::S_IFIFO | $mode, 0, sub { ...
492		779
		780	See C<aio_stat> for info about some potentially helpful extra constants
		781	and functions.
493		782
494	=item aio_link $srcpath, $dstpath, $callback->($status)	783	=item aio_link $srcpath, $dstpath, $callback->($status)
495		784
496	Asynchronously create a new link to the existing object at C<$srcpath> at	785	Asynchronously create a new link to the existing object at C<$srcpath> at
497	the path C<$dstpath> and call the callback with the result code.	786	the path C<$dstpath> and call the callback with the result code.
…		…
501		790
502	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at	791	Asynchronously create a new symbolic link to the existing object at C<$srcpath> at
503	the path C<$dstpath> and call the callback with the result code.	792	the path C<$dstpath> and call the callback with the result code.
504		793
505		794
506	=item aio_readlink $path, $callback->($link)	795	=item aio_readlink $pathname, $callback->($link)
507		796
508	Asynchronously read the symlink specified by C<$path> and pass it to	797	Asynchronously read the symlink specified by C<$path> and pass it to
509	the callback. If an error occurs, nothing or undef gets passed to the	798	the callback. If an error occurs, nothing or undef gets passed to the
510	callback.	799	callback.
511		800
512		801
		802	=item aio_realpath $pathname, $callback->($path)
		803
		804	Asynchronously make the path absolute and resolve any symlinks in
		805	C<$path>. The resulting path only consists of directories (same as
		806	L<Cwd::realpath>).
		807
		808	This request can be used to get the absolute path of the current working
		809	directory by passing it a path of F<.> (a single dot).
		810
		811
513	=item aio_rename $srcpath, $dstpath, $callback->($status)	812	=item aio_rename $srcpath, $dstpath, $callback->($status)
514		813
515	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as	814	Asynchronously rename the object at C<$srcpath> to C<$dstpath>, just as
516	rename(2) and call the callback with the result code.	815	rename(2) and call the callback with the result code.
		816
		817	On systems that support the AIO::WD working directory abstraction
		818	natively, the case C<[$wd, "."]> as C<$srcpath> is specialcased - instead
		819	of failing, C<rename> is called on the absolute path of C<$wd>.
		820
		821
		822	=item aio_rename2 $srcpath, $dstpath, $flags, $callback->($status)
		823
		824	Basically a version of C<aio_rename> with an additional C<$flags>
		825	argument. Calling this with C<$flags=0> is the same as calling
		826	C<aio_rename>.
		827
		828	Non-zero flags are currently only supported on GNU/Linux systems that
		829	support renameat2. Other systems fail with C<ENOSYS> in this case.
		830
		831	The following constants are available (missing ones are, as usual C<0>),
		832	see renameat2(2) for details:
		833
		834	C<IO::AIO::RENAME_NOREPLACE>, C<IO::AIO::RENAME_EXCHANGE>
		835	and C<IO::AIO::RENAME_WHITEOUT>.
517		836
518		837
519	=item aio_mkdir $pathname, $mode, $callback->($status)	838	=item aio_mkdir $pathname, $mode, $callback->($status)
520		839
521	Asynchronously mkdir (create) a directory and call the callback with	840	Asynchronously mkdir (create) a directory and call the callback with
…		…
526	=item aio_rmdir $pathname, $callback->($status)	845	=item aio_rmdir $pathname, $callback->($status)
527		846
528	Asynchronously rmdir (delete) a directory and call the callback with the	847	Asynchronously rmdir (delete) a directory and call the callback with the
529	result code.	848	result code.
530		849
		850	On systems that support the AIO::WD working directory abstraction
		851	natively, the case C<[$wd, "."]> is specialcased - instead of failing,
		852	C<rmdir> is called on the absolute path of C<$wd>.
		853
531		854
532	=item aio_readdir $pathname, $callback->($entries)	855	=item aio_readdir $pathname, $callback->($entries)
533		856
534	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire	857	Unlike the POSIX call of the same name, C<aio_readdir> reads an entire
535	directory (i.e. opendir + readdir + closedir). The entries will not be	858	directory (i.e. opendir + readdir + closedir). The entries will not be
…		…
539	array-ref with the filenames.	862	array-ref with the filenames.
540		863
541		864
542	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)	865	=item aio_readdirx $pathname, $flags, $callback->($entries, $flags)
543		866
544	Quite similar to C<aio_readdir>, but the C<$flags> argument allows to tune	867	Quite similar to C<aio_readdir>, but the C<$flags> argument allows one to
545	behaviour and output format. In case of an error, C<$entries> will be	868	tune behaviour and output format. In case of an error, C<$entries> will be
546	C<undef>.	869	C<undef>.
547		870
548	The flags are a combination of the following constants, ORed together (the	871	The flags are a combination of the following constants, ORed together (the
549	flags will also be passed to the callback, possibly modified):	872	flags will also be passed to the callback, possibly modified):
550		873
551	=over 4	874	=over 4
552		875
553	=item IO::AIO::READDIR_DENTS	876	=item IO::AIO::READDIR_DENTS
554		877
555	When this flag is off, then the callback gets an arrayref with of names	878	When this flag is off, then the callback gets an arrayref consisting of
556	only (as with C<aio_readdir>), otherwise it gets an arrayref with	879	names only (as with C<aio_readdir>), otherwise it gets an arrayref with
557	C<[$name, $type, $inode]> arrayrefs, each describing a single directory	880	C<[$name, $type, $inode]> arrayrefs, each describing a single directory
558	entry in more detail.	881	entry in more detail.
559		882
560	C<$name> is the name of the entry.	883	C<$name> is the name of the entry.
561		884
…		…
574	systems that do not deliver the inode information.	897	systems that do not deliver the inode information.
575		898
576	=item IO::AIO::READDIR_DIRS_FIRST	899	=item IO::AIO::READDIR_DIRS_FIRST
577		900
578	When this flag is set, then the names will be returned in an order where	901	When this flag is set, then the names will be returned in an order where
579	likely directories come first. This is useful when you need to quickly	902	likely directories come first, in optimal stat order. This is useful when
580	find directories, or you want to find all directories while avoiding to	903	you need to quickly find directories, or you want to find all directories
581	stat() each entry.	904	while avoiding to stat() each entry.
582		905
583	If the system returns type information in readdir, then this is used	906	If the system returns type information in readdir, then this is used
584	to find directories directly. Otherwise, likely directories are files	907	to find directories directly. Otherwise, likely directories are names
585	beginning with ".", or otherwise files with no dots, of which files with	908	beginning with ".", or otherwise names with no dots, of which names with
586	short names are tried first.	909	short names are tried first.
587		910
588	=item IO::AIO::READDIR_STAT_ORDER	911	=item IO::AIO::READDIR_STAT_ORDER
589		912
590	When this flag is set, then the names will be returned in an order	913	When this flag is set, then the names will be returned in an order
…		…
597		920
598	=item IO::AIO::READDIR_FOUND_UNKNOWN	921	=item IO::AIO::READDIR_FOUND_UNKNOWN
599		922
600	This flag should not be set when calling C<aio_readdirx>. Instead, it	923	This flag should not be set when calling C<aio_readdirx>. Instead, it
601	is being set by C<aio_readdirx>, when any of the C<$type>'s found were	924	is being set by C<aio_readdirx>, when any of the C<$type>'s found were
602	C<IO::AIO::DT_UNKNOWN>. The absense of this flag therefore indicates that all	925	C<IO::AIO::DT_UNKNOWN>. The absence of this flag therefore indicates that all
603	C<$type>'s are known, which can be used to speed up some algorithms.	926	C<$type>'s are known, which can be used to speed up some algorithms.
604		927
605	=back	928	=back
606		929
607		930
608	=item aio_load $path, $data, $callback->($status)	931	=item aio_load $pathname, $data, $callback->($status)
609		932
610	This is a composite request that tries to fully load the given file into	933	This is a composite request that tries to fully load the given file into
611	memory. Status is the same as with aio_read.	934	memory. Status is the same as with aio_read.
612		935
613	=cut	936	=cut
…		…
635		958
636	=item aio_copy $srcpath, $dstpath, $callback->($status)	959	=item aio_copy $srcpath, $dstpath, $callback->($status)
637		960
638	Try to copy the I<file> (directories not supported as either source or	961	Try to copy the I<file> (directories not supported as either source or
639	destination) from C<$srcpath> to C<$dstpath> and call the callback with	962	destination) from C<$srcpath> to C<$dstpath> and call the callback with
640	the C<0> (error) or C<-1> ok.	963	a status of C<0> (ok) or C<-1> (error, see C<$!>).
		964
		965	Existing destination files will be truncated.
641		966
642	This is a composite request that creates the destination file with	967	This is a composite request that creates the destination file with
643	mode 0200 and copies the contents of the source file into it using	968	mode 0200 and copies the contents of the source file into it using
644	C<aio_sendfile>, followed by restoring atime, mtime, access mode and	969	C<aio_sendfile>, followed by restoring atime, mtime, access mode and
645	uid/gid, in that order.	970	uid/gid, in that order.
…		…
657	my $grp = aio_group $cb;	982	my $grp = aio_group $cb;
658		983
659	aioreq_pri $pri;	984	aioreq_pri $pri;
660	add $grp aio_open $src, O_RDONLY, 0, sub {	985	add $grp aio_open $src, O_RDONLY, 0, sub {
661	if (my $src_fh = $_[0]) {	986	if (my $src_fh = $_[0]) {
662	my @stat = stat $src_fh; # hmm, might bock over nfs?	987	my @stat = stat $src_fh; # hmm, might block over nfs?
663		988
664	aioreq_pri $pri;	989	aioreq_pri $pri;
665	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {	990	add $grp aio_open $dst, O_CREAT | O_WRONLY | O_TRUNC, 0200, sub {
666	if (my $dst_fh = $_[0]) {	991	if (my $dst_fh = $_[0]) {
667	aioreq_pri $pri;	992	aioreq_pri $pri;
…		…
714		1039
715	=item aio_move $srcpath, $dstpath, $callback->($status)	1040	=item aio_move $srcpath, $dstpath, $callback->($status)
716		1041
717	Try to move the I<file> (directories not supported as either source or	1042	Try to move the I<file> (directories not supported as either source or
718	destination) from C<$srcpath> to C<$dstpath> and call the callback with	1043	destination) from C<$srcpath> to C<$dstpath> and call the callback with
719	the C<0> (error) or C<-1> ok.	1044	a status of C<0> (ok) or C<-1> (error, see C<$!>).
720		1045
721	This is a composite request that tries to rename(2) the file first; if	1046	This is a composite request that tries to rename(2) the file first; if
722	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if	1047	rename fails with C<EXDEV>, it copies the file with C<aio_copy> and, if
723	that is successful, unlinks the C<$srcpath>.	1048	that is successful, unlinks the C<$srcpath>.
724		1049
…		…
735	if ($_[0] && $! == EXDEV) {	1060	if ($_[0] && $! == EXDEV) {
736	aioreq_pri $pri;	1061	aioreq_pri $pri;
737	add $grp aio_copy $src, $dst, sub {	1062	add $grp aio_copy $src, $dst, sub {
738	$grp->result ($_[0]);	1063	$grp->result ($_[0]);
739		1064
740	if (!$_[0]) {	1065	unless ($_[0]) {
741	aioreq_pri $pri;	1066	aioreq_pri $pri;
742	add $grp aio_unlink $src;	1067	add $grp aio_unlink $src;
743	}	1068	}
744	};	1069	};
745	} else {	1070	} else {
…		…
748	};	1073	};
749		1074
750	$grp	1075	$grp
751	}	1076	}
752		1077
753	=item aio_scandir $path, $maxreq, $callback->($dirs, $nondirs)	1078	=item aio_scandir $pathname, $maxreq, $callback->($dirs, $nondirs)
754		1079
755	Scans a directory (similar to C<aio_readdir>) but additionally tries to	1080	Scans a directory (similar to C<aio_readdir>) but additionally tries to
756	efficiently separate the entries of directory C<$path> into two sets of	1081	efficiently separate the entries of directory C<$path> into two sets of
757	names, directories you can recurse into (directories), and ones you cannot	1082	names, directories you can recurse into (directories), and ones you cannot
758	recurse into (everything else, including symlinks to directories).	1083	recurse into (everything else, including symlinks to directories).
759		1084
760	C<aio_scandir> is a composite request that creates of many sub requests_	1085	C<aio_scandir> is a composite request that generates many sub requests.
761	C<$maxreq> specifies the maximum number of outstanding aio requests that	1086	C<$maxreq> specifies the maximum number of outstanding aio requests that
762	this function generates. If it is C<< <= 0 >>, then a suitable default	1087	this function generates. If it is C<< <= 0 >>, then a suitable default
763	will be chosen (currently 4).	1088	will be chosen (currently 4).
764		1089
765	On error, the callback is called without arguments, otherwise it receives	1090	On error, the callback is called without arguments, otherwise it receives
…		…
789	Then entries will be sorted into likely directories a non-initial dot	1114	Then entries will be sorted into likely directories a non-initial dot
790	currently) and likely non-directories (see C<aio_readdirx>). Then every	1115	currently) and likely non-directories (see C<aio_readdirx>). Then every
791	entry plus an appended C</.> will be C<stat>'ed, likely directories first,	1116	entry plus an appended C</.> will be C<stat>'ed, likely directories first,
792	in order of their inode numbers. If that succeeds, it assumes that the	1117	in order of their inode numbers. If that succeeds, it assumes that the
793	entry is a directory or a symlink to directory (which will be checked	1118	entry is a directory or a symlink to directory (which will be checked
794	seperately). This is often faster than stat'ing the entry itself because	1119	separately). This is often faster than stat'ing the entry itself because
795	filesystems might detect the type of the entry without reading the inode	1120	filesystems might detect the type of the entry without reading the inode
796	data (e.g. ext2fs filetype feature), even on systems that cannot return	1121	data (e.g. ext2fs filetype feature), even on systems that cannot return
797	the filetype information on readdir.	1122	the filetype information on readdir.
798		1123
799	If the known number of directories (link count - 2) has been reached, the	1124	If the known number of directories (link count - 2) has been reached, the
…		…
815		1140
816	my $grp = aio_group $cb;	1141	my $grp = aio_group $cb;
817		1142
818	$maxreq = 4 if $maxreq <= 0;	1143	$maxreq = 4 if $maxreq <= 0;
819		1144
820	# stat once	1145	# get a wd object
821	aioreq_pri $pri;	1146	aioreq_pri $pri;
822	add $grp aio_stat $path, sub {	1147	add $grp aio_wd $path, sub {
		1148	$_[0]
823	return $grp->result () if $_[0];	1149	or return $grp->result ();
824	my $now = time;
825	my $hash1 = join ":", (stat _)[0,1,3,7,9];
826		1150
827	# read the directory entries	1151	my $wd = [shift, "."];
		1152
		1153	# stat once
828	aioreq_pri $pri;	1154	aioreq_pri $pri;
829	add $grp aio_readdirx $path, READDIR_DIRS_FIRST, sub {	1155	add $grp aio_stat $wd, sub {
830	my $entries = shift
831	or return $grp->result ();	1156	return $grp->result () if $_[0];
		1157	my $now = time;
		1158	my $hash1 = join ":", (stat _)[0,1,3,7,9];
832		1159
833	# stat the dir another time	1160	# read the directory entries
834	aioreq_pri $pri;	1161	aioreq_pri $pri;
		1162	add $grp aio_readdirx $wd, READDIR_DIRS_FIRST, sub {
		1163	my $entries = shift
		1164	or return $grp->result ();
		1165
		1166	# stat the dir another time
		1167	aioreq_pri $pri;
835	add $grp aio_stat $path, sub {	1168	add $grp aio_stat $wd, sub {
836	my $hash2 = join ":", (stat _)[0,1,3,7,9];	1169	my $hash2 = join ":", (stat _)[0,1,3,7,9];
837		1170
838	my $ndirs;	1171	my $ndirs;
839		1172
840	# take the slow route if anything looks fishy	1173	# take the slow route if anything looks fishy
841	if ($hash1 ne $hash2 or (stat _)[9] == $now) {	1174	if ($hash1 ne $hash2 or (stat _)[9] == $now) {
842	$ndirs = -1;	1175	$ndirs = -1;
843	} else {	1176	} else {
844	# if nlink == 2, we are finished	1177	# if nlink == 2, we are finished
845	# for non-posix-fs's, we rely on nlink < 2	1178	# for non-posix-fs's, we rely on nlink < 2
846	$ndirs = (stat _)[3] - 2	1179	$ndirs = (stat _)[3] - 2
847	or return $grp->result ([], $entries);	1180	or return $grp->result ([], $entries);
848	}	1181	}
849		1182
850	my (@dirs, @nondirs);	1183	my (@dirs, @nondirs);
851		1184
852	my $statgrp = add $grp aio_group sub {	1185	my $statgrp = add $grp aio_group sub {
853	$grp->result (\@dirs, \@nondirs);	1186	$grp->result (\@dirs, \@nondirs);
854	};	1187	};
855		1188
856	limit $statgrp $maxreq;	1189	limit $statgrp $maxreq;
857	feed $statgrp sub {	1190	feed $statgrp sub {
858	return unless @$entries;	1191	return unless @$entries;
859	my $entry = shift @$entries;	1192	my $entry = shift @$entries;
860		1193
861	aioreq_pri $pri;	1194	aioreq_pri $pri;
		1195	$wd->[1] = "$entry/.";
862	add $statgrp aio_stat "$path/$entry/.", sub {	1196	add $statgrp aio_stat $wd, sub {
863	if ($_[0] < 0) {	1197	if ($_[0] < 0) {
864	push @nondirs, $entry;	1198	push @nondirs, $entry;
865	} else {	1199	} else {
866	# need to check for real directory	1200	# need to check for real directory
867	aioreq_pri $pri;	1201	aioreq_pri $pri;
		1202	$wd->[1] = $entry;
868	add $statgrp aio_lstat "$path/$entry", sub {	1203	add $statgrp aio_lstat $wd, sub {
869	if (-d _) {	1204	if (-d _) {
870	push @dirs, $entry;	1205	push @dirs, $entry;
871		1206
872	unless (--$ndirs) {	1207	unless (--$ndirs) {
873	push @nondirs, @$entries;	1208	push @nondirs, @$entries;
874	feed $statgrp;	1209	feed $statgrp;
		1210	}
		1211	} else {
		1212	push @nondirs, $entry;
875	}	1213	}
876	} else {
877	push @nondirs, $entry;
878	}	1214	}
879	}	1215	}
880	}	1216	};
881	};	1217	};
882	};	1218	};
883	};	1219	};
884	};	1220	};
885	};	1221	};
886		1222
887	$grp	1223	$grp
888	}	1224	}
889		1225
890	=item aio_rmtree $path, $callback->($status)	1226	=item aio_rmtree $pathname, $callback->($status)
891		1227
892	Delete a directory tree starting (and including) C<$path>, return the	1228	Delete a directory tree starting (and including) C<$path>, return the
893	status of the final C<rmdir> only. This is a composite request that	1229	status of the final C<rmdir> only. This is a composite request that
894	uses C<aio_scandir> to recurse into and rmdir directories, and unlink	1230	uses C<aio_scandir> to recurse into and rmdir directories, and unlink
895	everything else.	1231	everything else.
896		1232
897	=cut	1233	=cut
898		1234
…		…
920	};	1256	};
921		1257
922	$grp	1258	$grp
923	}	1259	}
924		1260
		1261	=item aio_fcntl $fh, $cmd, $arg, $callback->($status)
		1262
		1263	=item aio_ioctl $fh, $request, $buf, $callback->($status)
		1264
		1265	These work just like the C<fcntl> and C<ioctl> built-in functions, except
		1266	they execute asynchronously and pass the return value to the callback.
		1267
		1268	Both calls can be used for a lot of things, some of which make more sense
		1269	to run asynchronously in their own thread, while some others make less
		1270	sense. For example, calls that block waiting for external events, such
		1271	as locking, will also lock down an I/O thread while it is waiting, which
		1272	can deadlock the whole I/O system. At the same time, there might be no
		1273	alternative to using a thread to wait.
		1274
		1275	So in general, you should only use these calls for things that do
		1276	(filesystem) I/O, not for things that wait for other events (network,
		1277	other processes), although if you are careful and know what you are doing,
		1278	you still can.
		1279
		1280	The following constants are available (missing ones are, as usual C<0>):
		1281
		1282	C<F_DUPFD_CLOEXEC>,
		1283
		1284	C<F_OFD_GETLK>, C<F_OFD_SETLK>, C<F_OFD_GETLKW>,
		1285
		1286	C<FIFREEZE>, C<FITHAW>, C<FITRIM>, C<FICLONE>, C<FICLONERANGE>, C<FIDEDUPERANGE>.
		1287
		1288	C<FS_IOC_GETFLAGS>, C<FS_IOC_SETFLAGS>, C<FS_IOC_GETVERSION>, C<FS_IOC_SETVERSION>,
		1289	C<FS_IOC_FIEMAP>.
		1290
		1291	C<FS_IOC_FSGETXATTR>, C<FS_IOC_FSSETXATTR>, C<FS_IOC_SET_ENCRYPTION_POLICY>,
		1292	C<FS_IOC_GET_ENCRYPTION_PWSALT>, C<FS_IOC_GET_ENCRYPTION_POLICY>, C<FS_KEY_DESCRIPTOR_SIZE>.
		1293
		1294	C<FS_SECRM_FL>, C<FS_UNRM_FL>, C<FS_COMPR_FL>, C<FS_SYNC_FL>, C<FS_IMMUTABLE_FL>,
		1295	C<FS_APPEND_FL>, C<FS_NODUMP_FL>, C<FS_NOATIME_FL>, C<FS_DIRTY_FL>,
		1296	C<FS_COMPRBLK_FL>, C<FS_NOCOMP_FL>, C<FS_ENCRYPT_FL>, C<FS_BTREE_FL>,
		1297	C<FS_INDEX_FL>, C<FS_JOURNAL_DATA_FL>, C<FS_NOTAIL_FL>, C<FS_DIRSYNC_FL>, C<FS_TOPDIR_FL>,
		1298	C<FS_FL_USER_MODIFIABLE>.
		1299
		1300	C<FS_XFLAG_REALTIME>, C<FS_XFLAG_PREALLOC>, C<FS_XFLAG_IMMUTABLE>, C<FS_XFLAG_APPEND>,
		1301	C<FS_XFLAG_SYNC>, C<FS_XFLAG_NOATIME>, C<FS_XFLAG_NODUMP>, C<FS_XFLAG_RTINHERIT>,
		1302	C<FS_XFLAG_PROJINHERIT>, C<FS_XFLAG_NOSYMLINKS>, C<FS_XFLAG_EXTSIZE>, C<FS_XFLAG_EXTSZINHERIT>,
		1303	C<FS_XFLAG_NODEFRAG>, C<FS_XFLAG_FILESTREAM>, C<FS_XFLAG_DAX>, C<FS_XFLAG_HASATTR>,
		1304
925	=item aio_sync $callback->($status)	1305	=item aio_sync $callback->($status)
926		1306
927	Asynchronously call sync and call the callback when finished.	1307	Asynchronously call sync and call the callback when finished.
928		1308
929	=item aio_fsync $fh, $callback->($status)	1309	=item aio_fsync $fh, $callback->($status)
…		…
936	Asynchronously call fdatasync on the given filehandle and call the	1316	Asynchronously call fdatasync on the given filehandle and call the
937	callback with the fdatasync result code.	1317	callback with the fdatasync result code.
938		1318
939	If this call isn't available because your OS lacks it or it couldn't be	1319	If this call isn't available because your OS lacks it or it couldn't be
940	detected, it will be emulated by calling C<fsync> instead.	1320	detected, it will be emulated by calling C<fsync> instead.
		1321
		1322	=item aio_syncfs $fh, $callback->($status)
		1323
		1324	Asynchronously call the syncfs syscall to sync the filesystem associated
		1325	to the given filehandle and call the callback with the syncfs result
		1326	code. If syncfs is not available, calls sync(), but returns C<-1> and sets
		1327	errno to C<ENOSYS> nevertheless.
941		1328
942	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)	1329	=item aio_sync_file_range $fh, $offset, $nbytes, $flags, $callback->($status)
943		1330
944	Sync the data portion of the file specified by C<$offset> and C<$length>	1331	Sync the data portion of the file specified by C<$offset> and C<$length>
945	to disk (but NOT the metadata), by calling the Linux-specific	1332	to disk (but NOT the metadata), by calling the Linux-specific
…		…
949	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,	1336	C<$flags> can be a combination of C<IO::AIO::SYNC_FILE_RANGE_WAIT_BEFORE>,
950	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and	1337	C<IO::AIO::SYNC_FILE_RANGE_WRITE> and
951	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range	1338	C<IO::AIO::SYNC_FILE_RANGE_WAIT_AFTER>: refer to the sync_file_range
952	manpage for details.	1339	manpage for details.
953		1340
954	=item aio_pathsync $path, $callback->($status)	1341	=item aio_pathsync $pathname, $callback->($status)
955		1342
956	This request tries to open, fsync and close the given path. This is a	1343	This request tries to open, fsync and close the given path. This is a
957	composite request intended to sync directories after directory operations	1344	composite request intended to sync directories after directory operations
958	(E.g. rename). This might not work on all operating systems or have any	1345	(E.g. rename). This might not work on all operating systems or have any
959	specific effect, but usually it makes sure that directory changes get	1346	specific effect, but usually it makes sure that directory changes get
960	written to disc. It works for anything that can be opened for read-only,	1347	written to disc. It works for anything that can be opened for read-only,
961	not just directories.	1348	not just directories.
		1349
		1350	Future versions of this function might fall back to other methods when
		1351	C<fsync> on the directory fails (such as calling C<sync>).
962		1352
963	Passes C<0> when everything went ok, and C<-1> on error.	1353	Passes C<0> when everything went ok, and C<-1> on error.
964		1354
965	=cut	1355	=cut
966		1356
…		…
987	};	1377	};
988		1378
989	$grp	1379	$grp
990	}	1380	}
991		1381
		1382	=item aio_msync $scalar, $offset = 0, $length = undef, flags = MS_SYNC, $callback->($status)
		1383
		1384	This is a rather advanced IO::AIO call, which only works on mmap(2)ed
		1385	scalars (see the C<IO::AIO::mmap> function, although it also works on data
		1386	scalars managed by the L<Sys::Mmap> or L<Mmap> modules, note that the
		1387	scalar must only be modified in-place while an aio operation is pending on
		1388	it).
		1389
		1390	It calls the C<msync> function of your OS, if available, with the memory
		1391	area starting at C<$offset> in the string and ending C<$length> bytes
		1392	later. If C<$length> is negative, counts from the end, and if C<$length>
		1393	is C<undef>, then it goes till the end of the string. The flags can be
		1394	either C<IO::AIO::MS_ASYNC> or C<IO::AIO::MS_SYNC>, plus an optional
		1395	C<IO::AIO::MS_INVALIDATE>.
		1396
		1397	=item aio_mtouch $scalar, $offset = 0, $length = undef, flags = 0, $callback->($status)
		1398
		1399	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1400	scalars.
		1401
		1402	It touches (reads or writes) all memory pages in the specified
		1403	range inside the scalar. All caveats and parameters are the same
		1404	as for C<aio_msync>, above, except for flags, which must be either
		1405	C<0> (which reads all pages and ensures they are instantiated) or
		1406	C<IO::AIO::MT_MODIFY>, which modifies the memory pages (by reading and
		1407	writing an octet from it, which dirties the page).
		1408
		1409	=item aio_mlock $scalar, $offset = 0, $length = undef, $callback->($status)
		1410
		1411	This is a rather advanced IO::AIO call, which works best on mmap(2)ed
		1412	scalars.
		1413
		1414	It reads in all the pages of the underlying storage into memory (if any)
		1415	and locks them, so they are not getting swapped/paged out or removed.
		1416
		1417	If C<$length> is undefined, then the scalar will be locked till the end.
		1418
		1419	On systems that do not implement C<mlock>, this function returns C<-1>
		1420	and sets errno to C<ENOSYS>.
		1421
		1422	Note that the corresponding C<munlock> is synchronous and is
		1423	documented under L<MISCELLANEOUS FUNCTIONS>.
		1424
		1425	Example: open a file, mmap and mlock it - both will be undone when
		1426	C<$data> gets destroyed.
		1427
		1428	open my $fh, "<", $path or die "$path: $!";
		1429	my $data;
		1430	IO::AIO::mmap $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh;
		1431	aio_mlock $data; # mlock in background
		1432
		1433	=item aio_mlockall $flags, $callback->($status)
		1434
		1435	Calls the C<mlockall> function with the given C<$flags> (a combination of
		1436	C<IO::AIO::MCL_CURRENT> and C<IO::AIO::MCL_FUTURE>).
		1437
		1438	On systems that do not implement C<mlockall>, this function returns C<-1>
		1439	and sets errno to C<ENOSYS>.
		1440
		1441	Note that the corresponding C<munlockall> is synchronous and is
		1442	documented under L<MISCELLANEOUS FUNCTIONS>.
		1443
		1444	Example: asynchronously lock all current and future pages into memory.
		1445
		1446	aio_mlockall IO::AIO::MCL_FUTURE;
		1447
		1448	=item aio_fiemap $fh, $start, $length, $flags, $count, $cb->(\@extents)
		1449
		1450	Queries the extents of the given file (by calling the Linux C<FIEMAP>
		1451	ioctl, see L<http://cvs.schmorp.de/IO-AIO/doc/fiemap.txt> for details). If
		1452	the ioctl is not available on your OS, then this request will fail with
		1453	C<ENOSYS>.
		1454
		1455	C<$start> is the starting offset to query extents for, C<$length> is the
		1456	size of the range to query - if it is C<undef>, then the whole file will
		1457	be queried.
		1458
		1459	C<$flags> is a combination of flags (C<IO::AIO::FIEMAP_FLAG_SYNC> or
		1460	C<IO::AIO::FIEMAP_FLAG_XATTR> - C<IO::AIO::FIEMAP_FLAGS_COMPAT> is also
		1461	exported), and is normally C<0> or C<IO::AIO::FIEMAP_FLAG_SYNC> to query
		1462	the data portion.
		1463
		1464	C<$count> is the maximum number of extent records to return. If it is
		1465	C<undef>, then IO::AIO queries all extents of the range. As a very special
		1466	case, if it is C<0>, then the callback receives the number of extents
		1467	instead of the extents themselves (which is unreliable, see below).
		1468
		1469	If an error occurs, the callback receives no arguments. The special
		1470	C<errno> value C<IO::AIO::EBADR> is available to test for flag errors.
		1471
		1472	Otherwise, the callback receives an array reference with extent
		1473	structures. Each extent structure is an array reference itself, with the
		1474	following members:
		1475
		1476	[$logical, $physical, $length, $flags]
		1477
		1478	Flags is any combination of the following flag values (typically either C<0>
		1479	or C<IO::AIO::FIEMAP_EXTENT_LAST> (1)):
		1480
		1481	C<IO::AIO::FIEMAP_EXTENT_LAST>, C<IO::AIO::FIEMAP_EXTENT_UNKNOWN>,
		1482	C<IO::AIO::FIEMAP_EXTENT_DELALLOC>, C<IO::AIO::FIEMAP_EXTENT_ENCODED>,
		1483	C<IO::AIO::FIEMAP_EXTENT_DATA_ENCRYPTED>, C<IO::AIO::FIEMAP_EXTENT_NOT_ALIGNED>,
		1484	C<IO::AIO::FIEMAP_EXTENT_DATA_INLINE>, C<IO::AIO::FIEMAP_EXTENT_DATA_TAIL>,
		1485	C<IO::AIO::FIEMAP_EXTENT_UNWRITTEN>, C<IO::AIO::FIEMAP_EXTENT_MERGED> or
		1486	C<IO::AIO::FIEMAP_EXTENT_SHARED>.
		1487
		1488	At the time of this writing (Linux 3.2), this request is unreliable unless
		1489	C<$count> is C<undef>, as the kernel has all sorts of bugs preventing
		1490	it to return all extents of a range for files with a large number of
		1491	extents. The code (only) works around all these issues if C<$count> is
		1492	C<undef>.
		1493
992	=item aio_group $callback->(...)	1494	=item aio_group $callback->(...)
993		1495
994	This is a very special aio request: Instead of doing something, it is a	1496	This is a very special aio request: Instead of doing something, it is a
995	container for other aio requests, which is useful if you want to bundle	1497	container for other aio requests, which is useful if you want to bundle
996	many requests into a single, composite, request with a definite callback	1498	many requests into a single, composite, request with a definite callback
…		…
1032	like sleep and file handle readable/writable, the overhead this creates is	1534	like sleep and file handle readable/writable, the overhead this creates is
1033	immense (it blocks a thread for a long time) so do not use this function	1535	immense (it blocks a thread for a long time) so do not use this function
1034	except to put your application under artificial I/O pressure.	1536	except to put your application under artificial I/O pressure.
1035		1537
1036	=back	1538	=back
		1539
		1540
		1541	=head2 IO::AIO::WD - multiple working directories
		1542
		1543	Your process only has one current working directory, which is used by all
		1544	threads. This makes it hard to use relative paths (some other component
		1545	could call C<chdir> at any time, and it is hard to control when the path
		1546	will be used by IO::AIO).
		1547
		1548	One solution for this is to always use absolute paths. This usually works,
		1549	but can be quite slow (the kernel has to walk the whole path on every
		1550	access), and can also be a hassle to implement.
		1551
		1552	Newer POSIX systems have a number of functions (openat, fdopendir,
		1553	futimensat and so on) that make it possible to specify working directories
		1554	per operation.
		1555
		1556	For portability, and because the clowns who "designed", or shall I write,
		1557	perpetrated this new interface were obviously half-drunk, this abstraction
		1558	cannot be perfect, though.
		1559
		1560	IO::AIO allows you to convert directory paths into a so-called IO::AIO::WD
		1561	object. This object stores the canonicalised, absolute version of the
		1562	path, and on systems that allow it, also a directory file descriptor.
		1563
		1564	Everywhere where a pathname is accepted by IO::AIO (e.g. in C<aio_stat>
		1565	or C<aio_unlink>), one can specify an array reference with an IO::AIO::WD
		1566	object and a pathname instead (or the IO::AIO::WD object alone, which
		1567	gets interpreted as C<[$wd, "."]>). If the pathname is absolute, the
		1568	IO::AIO::WD object is ignored, otherwise the pathname is resolved relative
		1569	to that IO::AIO::WD object.
		1570
		1571	For example, to get a wd object for F</etc> and then stat F<passwd>
		1572	inside, you would write:
		1573
		1574	aio_wd "/etc", sub {
		1575	my $etcdir = shift;
		1576
		1577	# although $etcdir can be undef on error, there is generally no reason
		1578	# to check for errors here, as aio_stat will fail with ENOENT
		1579	# when $etcdir is undef.
		1580
		1581	aio_stat [$etcdir, "passwd"], sub {
		1582	# yay
		1583	};
		1584	};
		1585
		1586	The fact that C<aio_wd> is a request and not a normal function shows that
		1587	creating an IO::AIO::WD object is itself a potentially blocking operation,
		1588	which is why it is done asynchronously.
		1589
		1590	To stat the directory obtained with C<aio_wd> above, one could write
		1591	either of the following three request calls:
		1592
		1593	aio_lstat "/etc" , sub { ... # pathname as normal string
		1594	aio_lstat [$wd, "."], sub { ... # "." relative to $wd (i.e. $wd itself)
		1595	aio_lstat $wd , sub { ... # shorthand for the previous
		1596
		1597	As with normal pathnames, IO::AIO keeps a copy of the working directory
		1598	object and the pathname string, so you could write the following without
		1599	causing any issues due to C<$path> getting reused:
		1600
		1601	my $path = [$wd, undef];
		1602
		1603	for my $name (qw(abc def ghi)) {
		1604	$path->[1] = $name;
		1605	aio_stat $path, sub {
		1606	# ...
		1607	};
		1608	}
		1609
		1610	There are some caveats: when directories get renamed (or deleted), the
		1611	pathname string doesn't change, so will point to the new directory (or
		1612	nowhere at all), while the directory fd, if available on the system,
		1613	will still point to the original directory. Most functions accepting a
		1614	pathname will use the directory fd on newer systems, and the string on
		1615	older systems. Some functions (such as C<aio_realpath>) will always rely on
		1616	the string form of the pathname.
		1617
		1618	So this functionality is mainly useful to get some protection against
		1619	C<chdir>, to easily get an absolute path out of a relative path for future
		1620	reference, and to speed up doing many operations in the same directory
		1621	(e.g. when stat'ing all files in a directory).
		1622
		1623	The following functions implement this working directory abstraction:
		1624
		1625	=over 4
		1626
		1627	=item aio_wd $pathname, $callback->($wd)
		1628
		1629	Asynchonously canonicalise the given pathname and convert it to an
		1630	IO::AIO::WD object representing it. If possible and supported on the
		1631	system, also open a directory fd to speed up pathname resolution relative
		1632	to this working directory.
		1633
		1634	If something goes wrong, then C<undef> is passwd to the callback instead
		1635	of a working directory object and C<$!> is set appropriately. Since
		1636	passing C<undef> as working directory component of a pathname fails the
		1637	request with C<ENOENT>, there is often no need for error checking in the
		1638	C<aio_wd> callback, as future requests using the value will fail in the
		1639	expected way.
		1640
		1641	=item IO::AIO::CWD
		1642
		1643	This is a compiletime constant (object) that represents the process
		1644	current working directory.
		1645
		1646	Specifying this object as working directory object for a pathname is as if
		1647	the pathname would be specified directly, without a directory object. For
		1648	example, these calls are functionally identical:
		1649
		1650	aio_stat "somefile", sub { ... };
		1651	aio_stat [IO::AIO::CWD, "somefile"], sub { ... };
		1652
		1653	=back
		1654
		1655	To recover the path associated with an IO::AIO::WD object, you can use
		1656	C<aio_realpath>:
		1657
		1658	aio_realpath $wd, sub {
		1659	warn "path is $_[0]\n";
		1660	};
		1661
		1662	Currently, C<aio_statvfs> always, and C<aio_rename> and C<aio_rmdir>
		1663	sometimes, fall back to using an absolue path.
1037		1664
1038	=head2 IO::AIO::REQ CLASS	1665	=head2 IO::AIO::REQ CLASS
1039		1666
1040	All non-aggregate C<aio_*> functions return an object of this class when	1667	All non-aggregate C<aio_*> functions return an object of this class when
1041	called in non-void context.	1668	called in non-void context.
…		…
1131	=item $grp->cancel_subs	1758	=item $grp->cancel_subs
1132		1759
1133	Cancel all subrequests and clears any feeder, but not the group request	1760	Cancel all subrequests and clears any feeder, but not the group request
1134	itself. Useful when you queued a lot of events but got a result early.	1761	itself. Useful when you queued a lot of events but got a result early.
1135		1762
		1763	The group request will finish normally (you cannot add requests to the
		1764	group).
		1765
1136	=item $grp->result (...)	1766	=item $grp->result (...)
1137		1767
1138	Set the result value(s) that will be passed to the group callback when all	1768	Set the result value(s) that will be passed to the group callback when all
1139	subrequests have finished and set the groups errno to the current value	1769	subrequests have finished and set the groups errno to the current value
1140	of errno (just like calling C<errno> without an error number). By default,	1770	of errno (just like calling C<errno> without an error number). By default,
…		…
1156		1786
1157	Sets a feeder/generator on this group: every group can have an attached	1787	Sets a feeder/generator on this group: every group can have an attached
1158	generator that generates requests if idle. The idea behind this is that,	1788	generator that generates requests if idle. The idea behind this is that,
1159	although you could just queue as many requests as you want in a group,	1789	although you could just queue as many requests as you want in a group,
1160	this might starve other requests for a potentially long time. For example,	1790	this might starve other requests for a potentially long time. For example,
1161	C<aio_scandir> might generate hundreds of thousands C<aio_stat> requests,	1791	C<aio_scandir> might generate hundreds of thousands of C<aio_stat>
1162	delaying any later requests for a long time.	1792	requests, delaying any later requests for a long time.
1163		1793
1164	To avoid this, and allow incremental generation of requests, you can	1794	To avoid this, and allow incremental generation of requests, you can
1165	instead a group and set a feeder on it that generates those requests. The	1795	instead a group and set a feeder on it that generates those requests. The
1166	feed callback will be called whenever there are few enough (see C<limit>,	1796	feed callback will be called whenever there are few enough (see C<limit>,
1167	below) requests active in the group itself and is expected to queue more	1797	below) requests active in the group itself and is expected to queue more
…		…
1208	=over 4	1838	=over 4
1209		1839
1210	=item $fileno = IO::AIO::poll_fileno	1840	=item $fileno = IO::AIO::poll_fileno
1211		1841
1212	Return the I<request result pipe file descriptor>. This filehandle must be	1842	Return the I<request result pipe file descriptor>. This filehandle must be
1213	polled for reading by some mechanism outside this module (e.g. Event or	1843	polled for reading by some mechanism outside this module (e.g. EV, Glib,
1214	select, see below or the SYNOPSIS). If the pipe becomes readable you have	1844	select and so on, see below or the SYNOPSIS). If the pipe becomes readable
1215	to call C<poll_cb> to check the results.	1845	you have to call C<poll_cb> to check the results.
1216		1846
1217	See C<poll_cb> for an example.	1847	See C<poll_cb> for an example.
1218		1848
1219	=item IO::AIO::poll_cb	1849	=item IO::AIO::poll_cb
1220		1850
1221	Process some outstanding events on the result pipe. You have to call this	1851	Process some requests that have reached the result phase (i.e. they have
1222	regularly. Returns C<0> if all events could be processed, or C<-1> if it	1852	been executed but the results are not yet reported). You have to call
1223	returned earlier for whatever reason. Returns immediately when no events	1853	this "regularly" to finish outstanding requests.
1224	are outstanding. The amount of events processed depends on the settings of
1225	C<IO::AIO::max_poll_req> and C<IO::AIO::max_poll_time>.
1226		1854
		1855	Returns C<0> if all events could be processed (or there were no
		1856	events to process), or C<-1> if it returned earlier for whatever
		1857	reason. Returns immediately when no events are outstanding. The amount
		1858	of events processed depends on the settings of C<IO::AIO::max_poll_req>,
		1859	C<IO::AIO::max_poll_time> and C<IO::AIO::max_outstanding>.
		1860
1227	If not all requests were processed for whatever reason, the filehandle	1861	If not all requests were processed for whatever reason, the poll file
1228	will still be ready when C<poll_cb> returns, so normally you don't have to	1862	descriptor will still be ready when C<poll_cb> returns, so normally you
1229	do anything special to have it called later.	1863	don't have to do anything special to have it called later.
		1864
		1865	Apart from calling C<IO::AIO::poll_cb> when the event filehandle becomes
		1866	ready, it can be beneficial to call this function from loops which submit
		1867	a lot of requests, to make sure the results get processed when they become
		1868	available and not just when the loop is finished and the event loop takes
		1869	over again. This function returns very fast when there are no outstanding
		1870	requests.
1230		1871
1231	Example: Install an Event watcher that automatically calls	1872	Example: Install an Event watcher that automatically calls
1232	IO::AIO::poll_cb with high priority:	1873	IO::AIO::poll_cb with high priority (more examples can be found in the
		1874	SYNOPSIS section, at the top of this document):
1233		1875
1234	Event->io (fd => IO::AIO::poll_fileno,	1876	Event->io (fd => IO::AIO::poll_fileno,
1235	poll => 'r', async => 1,	1877	poll => 'r', async => 1,
1236	cb => \&IO::AIO::poll_cb);	1878	cb => \&IO::AIO::poll_cb);
		1879
		1880	=item IO::AIO::poll_wait
		1881
		1882	Wait until either at least one request is in the result phase or no
		1883	requests are outstanding anymore.
		1884
		1885	This is useful if you want to synchronously wait for some requests to
		1886	become ready, without actually handling them.
		1887
		1888	See C<nreqs> for an example.
		1889
		1890	=item IO::AIO::poll
		1891
		1892	Waits until some requests have been handled.
		1893
		1894	Returns the number of requests processed, but is otherwise strictly
		1895	equivalent to:
		1896
		1897	IO::AIO::poll_wait, IO::AIO::poll_cb
		1898
		1899	=item IO::AIO::flush
		1900
		1901	Wait till all outstanding AIO requests have been handled.
		1902
		1903	Strictly equivalent to:
		1904
		1905	IO::AIO::poll_wait, IO::AIO::poll_cb
		1906	while IO::AIO::nreqs;
1237		1907
1238	=item IO::AIO::max_poll_reqs $nreqs	1908	=item IO::AIO::max_poll_reqs $nreqs
1239		1909
1240	=item IO::AIO::max_poll_time $seconds	1910	=item IO::AIO::max_poll_time $seconds
1241		1911
…		…
1266	# use a low priority so other tasks have priority	1936	# use a low priority so other tasks have priority
1267	Event->io (fd => IO::AIO::poll_fileno,	1937	Event->io (fd => IO::AIO::poll_fileno,
1268	poll => 'r', nice => 1,	1938	poll => 'r', nice => 1,
1269	cb => &IO::AIO::poll_cb);	1939	cb => &IO::AIO::poll_cb);
1270		1940
1271	=item IO::AIO::poll_wait
1272
1273	If there are any outstanding requests and none of them in the result
1274	phase, wait till the result filehandle becomes ready for reading (simply
1275	does a C<select> on the filehandle. This is useful if you want to
1276	synchronously wait for some requests to finish).
1277
1278	See C<nreqs> for an example.
1279
1280	=item IO::AIO::poll
1281
1282	Waits until some requests have been handled.
1283
1284	Returns the number of requests processed, but is otherwise strictly
1285	equivalent to:
1286
1287	IO::AIO::poll_wait, IO::AIO::poll_cb
1288
1289	=item IO::AIO::flush
1290
1291	Wait till all outstanding AIO requests have been handled.
1292
1293	Strictly equivalent to:
1294
1295	IO::AIO::poll_wait, IO::AIO::poll_cb
1296	while IO::AIO::nreqs;
1297
1298	=back	1941	=back
1299		1942
1300	=head3 CONTROLLING THE NUMBER OF THREADS	1943	=head3 CONTROLLING THE NUMBER OF THREADS
1301		1944
1302	=over	1945	=over
…		…
1335		1978
1336	Under normal circumstances you don't need to call this function.	1979	Under normal circumstances you don't need to call this function.
1337		1980
1338	=item IO::AIO::max_idle $nthreads	1981	=item IO::AIO::max_idle $nthreads
1339		1982
1340	Limit the number of threads (default: 4) that are allowed to idle (i.e.,	1983	Limit the number of threads (default: 4) that are allowed to idle
1341	threads that did not get a request to process within 10 seconds). That	1984	(i.e., threads that did not get a request to process within the idle
1342	means if a thread becomes idle while C<$nthreads> other threads are also	1985	timeout (default: 10 seconds). That means if a thread becomes idle while
1343	idle, it will free its resources and exit.	1986	C<$nthreads> other threads are also idle, it will free its resources and
		1987	exit.
1344		1988
1345	This is useful when you allow a large number of threads (e.g. 100 or 1000)	1989	This is useful when you allow a large number of threads (e.g. 100 or 1000)
1346	to allow for extremely high load situations, but want to free resources	1990	to allow for extremely high load situations, but want to free resources
1347	under normal circumstances (1000 threads can easily consume 30MB of RAM).	1991	under normal circumstances (1000 threads can easily consume 30MB of RAM).
1348		1992
1349	The default is probably ok in most situations, especially if thread	1993	The default is probably ok in most situations, especially if thread
1350	creation is fast. If thread creation is very slow on your system you might	1994	creation is fast. If thread creation is very slow on your system you might
1351	want to use larger values.	1995	want to use larger values.
1352		1996
		1997	=item IO::AIO::idle_timeout $seconds
		1998
		1999	Sets the minimum idle timeout (default 10) after which worker threads are
		2000	allowed to exit. SEe C<IO::AIO::max_idle>.
		2001
1353	=item IO::AIO::max_outstanding $maxreqs	2002	=item IO::AIO::max_outstanding $maxreqs
		2003
		2004	Sets the maximum number of outstanding requests to C<$nreqs>. If
		2005	you do queue up more than this number of requests, the next call to
		2006	C<IO::AIO::poll_cb> (and other functions calling C<poll_cb>, such as
		2007	C<IO::AIO::flush> or C<IO::AIO::poll>) will block until the limit is no
		2008	longer exceeded.
		2009
		2010	In other words, this setting does not enforce a queue limit, but can be
		2011	used to make poll functions block if the limit is exceeded.
1354		2012
1355	This is a very bad function to use in interactive programs because it	2013	This is a very bad function to use in interactive programs because it
1356	blocks, and a bad way to reduce concurrency because it is inexact: Better	2014	blocks, and a bad way to reduce concurrency because it is inexact: Better
1357	use an C<aio_group> together with a feed callback.	2015	use an C<aio_group> together with a feed callback.
1358		2016
1359	Sets the maximum number of outstanding requests to C<$nreqs>. If you	2017	Its main use is in scripts without an event loop - when you want to stat
1360	do queue up more than this number of requests, the next call to the	2018	a lot of files, you can write something like this:
1361	C<poll_cb> (and C<poll_some> and other functions calling C<poll_cb>)
1362	function will block until the limit is no longer exceeded.
1363		2019
1364	The default value is very large, so there is no practical limit on the	2020	IO::AIO::max_outstanding 32;
1365	number of outstanding requests.
1366		2021
1367	You can still queue as many requests as you want. Therefore,	2022	for my $path (...) {
1368	C<max_outstanding> is mainly useful in simple scripts (with low values) or	2023	aio_stat $path , ...;
1369	as a stop gap to shield against fatal memory overflow (with large values).	2024	IO::AIO::poll_cb;
		2025	}
		2026
		2027	IO::AIO::flush;
		2028
		2029	The call to C<poll_cb> inside the loop will normally return instantly, but
		2030	as soon as more thna C<32> reqeusts are in-flight, it will block until
		2031	some requests have been handled. This keeps the loop from pushing a large
		2032	number of C<aio_stat> requests onto the queue.
		2033
		2034	The default value for C<max_outstanding> is very large, so there is no
		2035	practical limit on the number of outstanding requests.
1370		2036
1371	=back	2037	=back
1372		2038
1373	=head3 STATISTICAL INFORMATION	2039	=head3 STATISTICAL INFORMATION
1374		2040
…		…
1394	Returns the number of requests currently in the pending state (executed,	2060	Returns the number of requests currently in the pending state (executed,
1395	but not yet processed by poll_cb).	2061	but not yet processed by poll_cb).
1396		2062
1397	=back	2063	=back
1398		2064
		2065	=head3 MISCELLANEOUS FUNCTIONS
		2066
		2067	IO::AIO implements some functions that are useful when you want to use
		2068	some "Advanced I/O" function not available to in Perl, without going the
		2069	"Asynchronous I/O" route. Many of these have an asynchronous C<aio_*>
		2070	counterpart.
		2071
		2072	=over 4
		2073
		2074	=item $numfd = IO::AIO::get_fdlimit
		2075
		2076	This function is I<EXPERIMENTAL> and subject to change.
		2077
		2078	Tries to find the current file descriptor limit and returns it, or
		2079	C<undef> and sets C<$!> in case of an error. The limit is one larger than
		2080	the highest valid file descriptor number.
		2081
		2082	=item IO::AIO::min_fdlimit [$numfd]
		2083
		2084	This function is I<EXPERIMENTAL> and subject to change.
		2085
		2086	Try to increase the current file descriptor limit(s) to at least C<$numfd>
		2087	by changing the soft or hard file descriptor resource limit. If C<$numfd>
		2088	is missing, it will try to set a very high limit, although this is not
		2089	recommended when you know the actual minimum that you require.
		2090
		2091	If the limit cannot be raised enough, the function makes a best-effort
		2092	attempt to increase the limit as much as possible, using various
		2093	tricks, while still failing. You can query the resulting limit using
		2094	C<IO::AIO::get_fdlimit>.
		2095
		2096	If an error occurs, returns C<undef> and sets C<$!>, otherwise returns
		2097	true.
		2098
		2099	=item IO::AIO::sendfile $ofh, $ifh, $offset, $count
		2100
		2101	Calls the C<eio_sendfile_sync> function, which is like C<aio_sendfile>,
		2102	but is blocking (this makes most sense if you know the input data is
		2103	likely cached already and the output filehandle is set to non-blocking
		2104	operations).
		2105
		2106	Returns the number of bytes copied, or C<-1> on error.
		2107
		2108	=item IO::AIO::fadvise $fh, $offset, $len, $advice
		2109
		2110	Simply calls the C<posix_fadvise> function (see its
		2111	manpage for details). The following advice constants are
		2112	available: C<IO::AIO::FADV_NORMAL>, C<IO::AIO::FADV_SEQUENTIAL>,
		2113	C<IO::AIO::FADV_RANDOM>, C<IO::AIO::FADV_NOREUSE>,
		2114	C<IO::AIO::FADV_WILLNEED>, C<IO::AIO::FADV_DONTNEED>.
		2115
		2116	On systems that do not implement C<posix_fadvise>, this function returns
		2117	ENOSYS, otherwise the return value of C<posix_fadvise>.
		2118
		2119	=item IO::AIO::madvise $scalar, $offset, $len, $advice
		2120
		2121	Simply calls the C<posix_madvise> function (see its
		2122	manpage for details). The following advice constants are
		2123	available: C<IO::AIO::MADV_NORMAL>, C<IO::AIO::MADV_SEQUENTIAL>,
		2124	C<IO::AIO::MADV_RANDOM>, C<IO::AIO::MADV_WILLNEED>,
		2125	C<IO::AIO::MADV_DONTNEED>.
		2126
		2127	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2128	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2129	will be reduced to fit into the C<$scalar>.
		2130
		2131	On systems that do not implement C<posix_madvise>, this function returns
		2132	ENOSYS, otherwise the return value of C<posix_madvise>.
		2133
		2134	=item IO::AIO::mprotect $scalar, $offset, $len, $protect
		2135
		2136	Simply calls the C<mprotect> function on the preferably AIO::mmap'ed
		2137	$scalar (see its manpage for details). The following protect
		2138	constants are available: C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_READ>,
		2139	C<IO::AIO::PROT_WRITE>, C<IO::AIO::PROT_EXEC>.
		2140
		2141	If C<$offset> is negative, counts from the end. If C<$length> is negative,
		2142	the remaining length of the C<$scalar> is used. If possible, C<$length>
		2143	will be reduced to fit into the C<$scalar>.
		2144
		2145	On systems that do not implement C<mprotect>, this function returns
		2146	ENOSYS, otherwise the return value of C<mprotect>.
		2147
		2148	=item IO::AIO::mmap $scalar, $length, $prot, $flags, $fh[, $offset]
		2149
		2150	Memory-maps a file (or anonymous memory range) and attaches it to the
		2151	given C<$scalar>, which will act like a string scalar. Returns true on
		2152	success, and false otherwise.
		2153
		2154	The scalar must exist, but its contents do not matter - this means you
		2155	cannot use a nonexistant array or hash element. When in doubt, C<undef>
		2156	the scalar first.
		2157
		2158	The only operations allowed on the mmapped scalar are C<substr>/C<vec>,
		2159	which don't change the string length, and most read-only operations such
		2160	as copying it or searching it with regexes and so on.
		2161
		2162	Anything else is unsafe and will, at best, result in memory leaks.
		2163
		2164	The memory map associated with the C<$scalar> is automatically removed
		2165	when the C<$scalar> is undef'd or destroyed, or when the C<IO::AIO::mmap>
		2166	or C<IO::AIO::munmap> functions are called on it.
		2167
		2168	This calls the C<mmap>(2) function internally. See your system's manual
		2169	page for details on the C<$length>, C<$prot> and C<$flags> parameters.
		2170
		2171	The C<$length> must be larger than zero and smaller than the actual
		2172	filesize.
		2173
		2174	C<$prot> is a combination of C<IO::AIO::PROT_NONE>, C<IO::AIO::PROT_EXEC>,
		2175	C<IO::AIO::PROT_READ> and/or C<IO::AIO::PROT_WRITE>,
		2176
		2177	C<$flags> can be a combination of
		2178	C<IO::AIO::MAP_SHARED> or
		2179	C<IO::AIO::MAP_PRIVATE>,
		2180	or a number of system-specific flags (when not available, the are C<0>):
		2181	C<IO::AIO::MAP_ANONYMOUS> (which is set to C<MAP_ANON> if your system only provides this constant),
		2182	C<IO::AIO::MAP_LOCKED>,
		2183	C<IO::AIO::MAP_NORESERVE>,
		2184	C<IO::AIO::MAP_POPULATE>,
		2185	C<IO::AIO::MAP_NONBLOCK>,
		2186	C<IO::AIO::MAP_FIXED>,
		2187	C<IO::AIO::MAP_GROWSDOWN>,
		2188	C<IO::AIO::MAP_32BIT>,
		2189	C<IO::AIO::MAP_HUGETLB> or
		2190	C<IO::AIO::MAP_STACK>.
		2191
		2192	If C<$fh> is C<undef>, then a file descriptor of C<-1> is passed.
		2193
		2194	C<$offset> is the offset from the start of the file - it generally must be
		2195	a multiple of C<IO::AIO::PAGESIZE> and defaults to C<0>.
		2196
		2197	Example:
		2198
		2199	use Digest::MD5;
		2200	use IO::AIO;
		2201
		2202	open my $fh, "<verybigfile"
		2203	or die "$!";
		2204
		2205	IO::AIO::mmap my $data, -s $fh, IO::AIO::PROT_READ, IO::AIO::MAP_SHARED, $fh
		2206	or die "verybigfile: $!";
		2207
		2208	my $fast_md5 = md5 $data;
		2209
		2210	=item IO::AIO::munmap $scalar
		2211
		2212	Removes a previous mmap and undefines the C<$scalar>.
		2213
		2214	=item IO::AIO::munlock $scalar, $offset = 0, $length = undef
		2215
		2216	Calls the C<munlock> function, undoing the effects of a previous
		2217	C<aio_mlock> call (see its description for details).
		2218
		2219	=item IO::AIO::munlockall
		2220
		2221	Calls the C<munlockall> function.
		2222
		2223	On systems that do not implement C<munlockall>, this function returns
		2224	ENOSYS, otherwise the return value of C<munlockall>.
		2225
		2226	=item IO::AIO::splice $r_fh, $r_off, $w_fh, $w_off, $length, $flags
		2227
		2228	Calls the GNU/Linux C<splice(2)> syscall, if available. If C<$r_off> or
		2229	C<$w_off> are C<undef>, then C<NULL> is passed for these, otherwise they
		2230	should be the file offset.
		2231
		2232	C<$r_fh> and C<$w_fh> should not refer to the same file, as splice might
		2233	silently corrupt the data in this case.
		2234
		2235	The following symbol flag values are available: C<IO::AIO::SPLICE_F_MOVE>,
		2236	C<IO::AIO::SPLICE_F_NONBLOCK>, C<IO::AIO::SPLICE_F_MORE> and
		2237	C<IO::AIO::SPLICE_F_GIFT>.
		2238
		2239	See the C<splice(2)> manpage for details.
		2240
		2241	=item IO::AIO::tee $r_fh, $w_fh, $length, $flags
		2242
		2243	Calls the GNU/Linux C<tee(2)> syscall, see its manpage and the
		2244	description for C<IO::AIO::splice> above for details.
		2245
		2246	=item $actual_size = IO::AIO::pipesize $r_fh[, $new_size]
		2247
		2248	Attempts to query or change the pipe buffer size. Obviously works only
		2249	on pipes, and currently works only on GNU/Linux systems, and fails with
		2250	C<-1>/C<ENOSYS> everywhere else. If anybody knows how to influence pipe buffer
		2251	size on other systems, drop me a note.
		2252
		2253	=item ($rfh, $wfh) = IO::AIO::pipe2 [$flags]
		2254
		2255	This is a direct interface to the Linux L<pipe2(2)> system call. If
		2256	C<$flags> is missing or C<0>, then this should be the same as a call to
		2257	perl's built-in C<pipe> function and create a new pipe, and works on
		2258	systems that lack the pipe2 syscall. On win32, this case invokes C<_pipe
		2259	(..., 4096, O_BINARY)>.
		2260
		2261	If C<$flags> is non-zero, it tries to invoke the pipe2 system call with
		2262	the given flags (Linux 2.6.27, glibc 2.9).
		2263
		2264	On success, the read and write file handles are returned.
		2265
		2266	On error, nothing will be returned. If the pipe2 syscall is missing and
		2267	C<$flags> is non-zero, fails with C<ENOSYS>.
		2268
		2269	Please refer to L<pipe2(2)> for more info on the C<$flags>, but at the
		2270	time of this writing, C<IO::AIO::O_CLOEXEC>, C<IO::AIO::O_NONBLOCK> and
		2271	C<IO::AIO::O_DIRECT> (Linux 3.4, for packet-based pipes) were supported.
		2272
		2273	=back
		2274
1399	=cut	2275	=cut
1400		2276
1401	min_parallel 8;	2277	min_parallel 8;
1402		2278
1403	END { flush }	2279	END { flush }
1404		2280
1405	1;	2281	1;
1406		2282
		2283	=head1 EVENT LOOP INTEGRATION
		2284
		2285	It is recommended to use L<AnyEvent::AIO> to integrate IO::AIO
		2286	automatically into many event loops:
		2287
		2288	# AnyEvent integration (EV, Event, Glib, Tk, POE, urxvt, pureperl...)
		2289	use AnyEvent::AIO;
		2290
		2291	You can also integrate IO::AIO manually into many event loops, here are
		2292	some examples of how to do this:
		2293
		2294	# EV integration
		2295	my $aio_w = EV::io IO::AIO::poll_fileno, EV::READ, \&IO::AIO::poll_cb;
		2296
		2297	# Event integration
		2298	Event->io (fd => IO::AIO::poll_fileno,
		2299	poll => 'r',
		2300	cb => \&IO::AIO::poll_cb);
		2301
		2302	# Glib/Gtk2 integration
		2303	add_watch Glib::IO IO::AIO::poll_fileno,
		2304	in => sub { IO::AIO::poll_cb; 1 };
		2305
		2306	# Tk integration
		2307	Tk::Event::IO->fileevent (IO::AIO::poll_fileno, "",
		2308	readable => \&IO::AIO::poll_cb);
		2309
		2310	# Danga::Socket integration
		2311	Danga::Socket->AddOtherFds (IO::AIO::poll_fileno =>
		2312	\&IO::AIO::poll_cb);
		2313
1407	=head2 FORK BEHAVIOUR	2314	=head2 FORK BEHAVIOUR
1408		2315
1409	This module should do "the right thing" when the process using it forks:	2316	Usage of pthreads in a program changes the semantics of fork
		2317	considerably. Specifically, only async-safe functions can be called after
		2318	fork. Perl doesn't know about this, so in general, you cannot call fork
		2319	with defined behaviour in perl if pthreads are involved. IO::AIO uses
		2320	pthreads, so this applies, but many other extensions and (for inexplicable
		2321	reasons) perl itself often is linked against pthreads, so this limitation
		2322	applies to quite a lot of perls.
1410		2323
1411	Before the fork, IO::AIO enters a quiescent state where no requests	2324	This module no longer tries to fight your OS, or POSIX. That means IO::AIO
1412	can be added in other threads and no results will be processed. After	2325	only works in the process that loaded it. Forking is fully supported, but
1413	the fork the parent simply leaves the quiescent state and continues	2326	using IO::AIO in the child is not.
1414	request/result processing, while the child frees the request/result queue
1415	(so that the requests started before the fork will only be handled in the
1416	parent). Threads will be started on demand until the limit set in the
1417	parent process has been reached again.
1418		2327
1419	In short: the parent will, after a short pause, continue as if fork had	2328	You might get around by not I<using> IO::AIO before (or after)
1420	not been called, while the child will act as if IO::AIO has not been used	2329	forking. You could also try to call the L<IO::AIO::reinit> function in the
1421	yet.	2330	child:
		2331
		2332	=over 4
		2333
		2334	=item IO::AIO::reinit
		2335
		2336	Abandons all current requests and I/O threads and simply reinitialises all
		2337	data structures. This is not an operation supported by any standards, but
		2338	happens to work on GNU/Linux and some newer BSD systems.
		2339
		2340	The only reasonable use for this function is to call it after forking, if
		2341	C<IO::AIO> was used in the parent. Calling it while IO::AIO is active in
		2342	the process will result in undefined behaviour. Calling it at any time
		2343	will also result in any undefined (by POSIX) behaviour.
		2344
		2345	=back
1422		2346
1423	=head2 MEMORY USAGE	2347	=head2 MEMORY USAGE
1424		2348
1425	Per-request usage:	2349	Per-request usage:
1426		2350

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